Method of making improved gum base for fruit-flavored chewing gum

ABSTRACT

A method is provided for preparing a gum base which enhances the long-term flavor intensity of a free fruit-flavored chewing gum. A water-insoluble restrainer is added to the gum base in an amount sufficient to constitute at least 7% by weight of the chewing gum or four times the weight percentage of the free fruit flavor ingredient in the chewing gum to which the gum base will be added. The properly selected restrainer will have a solubility parameter within ±2.0[J/M 3  ] 1/2  ×10 -3  of the Solubility Parameter of the free fruit flavoring agent whose flavor is being enhanced, preferably within ±1.0[J/M 3  ] 1/2  ×10 -3  of the Solubility Parameter of the free fruit flavoring agent.

FIELD OF THE INVENTION

This invention relates to a method of making an improved gum base foruse in a free fruit-flavored chewing gum, and to a gum base madeaccording to this method. Free fruit-flavored chewing gum made using thegum base of the invention has an enhanced long-term flavor intensitywithout sacrificing the initial flavor burst, and without requiring theuse of certain flavor encapsulation techniques.

BACKGROUND OF THE INVENTION

Solubility is believed to occur between materials, for example, asolvent and a polymer, when the Gibbs free energy of mixing is less thanzero. The energy of mixing is discussed by Dr. Billmeyer in the"Textbook Of Polymer Science", Second Edition, John Wiley and Sons, Inc.(1975), pages 24-26, the disclosure of which is incorporated herein byreference. As explained by Dr. Billmeyer, the free energy of mixing ΔGis defined according to the following equation:

    ΔG=ΔH-TΔS,

wherein ΔH represents the enthalpy of mixing, ΔS represents the entropyof mixing, and T is the absolute temperature.

For reasonably nonpolar molecules, and where the degree of hydrogenbonding is insignificant or nonexistent, the enthalpy of mixing ispositive and can be derived from the following equation:

    ΔH=V.sub.1 V.sub.2 (δ.sub.1 -δ.sub.2).sup.2,

wherein V is the volume fraction and subscripts 1 and 2 refer to thesolvent and the polymer, respectively. The quantity δ² is the cohesiveenergy density of an ingredient. The quantity δ, which represents thesquare root of the cohesive energy density, is known as the SolubilityParameter.

Generally, in the absence of significant hydrogen bonding, solubilitycan be expected to occur between a solvent and a polymer if thedifference in Solubility Parameters (δ₁ -δ₂) is less than about 1.7-2.0.In other words, materials having similar Solubility Parameters tend toreach thermodynamic equilibrium when they are mixed together, and thistendency toward equilibrium causes the different molecules to attractand mix with each other. Materials having dissimilar SolubilityParameters tend to reach thermodynamic equilibrium when separated, andthis causes the different molecules to repel and separate from eachother.

The Solubility Parameters of different substances have been the subjectof various calculations and publications. For a polymer, a relativelyeasy way to determine δ₂ is from a summation of molar attractionconstants multiplied by the density and divided by the repeating unitmolecular weight: ##EQU1## wherein Σ is the summation operator, E_(i) isthe molar attraction constant for each chemical moiety making up therepeating unit, M. W. is the molecular weight of the repeating unit, andρ is the polymer density.

The Solubility Parameter (δ₁ or δ₂) can be expressed in SolubilityParameter Units (S.P.U.'s), with one S.P.U. being equal to one [J/m³]^(1/2) ×10⁻³, where J=Joules and m=meters. For a more detailedexplanation of the Solubility Parameter and its values for variouscompounds, see the Third Edition of "Polymer Handbook", edited byBandrup and Immergut, and published by John Wiley and Sons, Inc., NewYork, N.Y., in 1989. The chapter of the "Polymer Handbook", beginning onpage VII/519, and entitled "Solubility Parameters", is incorporatedherein by reference.

Fruit-flavored chewing gums (whether they be wax-containing or wax-free)have a well-known characteristic or problem of rapid flavor release andshort flavor duration. Fruit-flavored chewing gums have a tendency toexhibit a very rapid flavor release in the early stages of chewing,followed by rapid dissipation until the fruit flavor becomes virtuallyundetectable after 8-12 minutes of chewing.

This problem has been addressed in the prior art by using certainencapsulation techniques for slowing the release of fruit flavors.However, these encapsulation techniques present an additional problem inthat they operate by creating a physical barrier to modify the releaseof fruit flavors. Also, the pleasing initial flavor burst associatedwith fruit-flavored gum is, to some extent, sacrificed when theseencapsulation techniques are used. Additionally, it is known that alarge percentage of the fruit flavor initially added to the chewing gum(in some cases, up to 60%) is never actually tasted by the consumer.

In order to provide a pleasing long-lasting flavor to a free fruitflavored chewing gum, it is generally desirable to prolong the timeperiod during which at least 15% of the original flavor intensity isapparent to the consumer. In other words, the consumer initially detectsa flavor burst of a relatively high intensity when chewing is commenced.Thereafter, the detected flavor intensity inevitably declines with timeduring chewing. When the detected flavor intensity decreases by morethan 85% from the original level, the gum becomes annoyingly low intaste and is less pleasant to chew. Therefore, the enjoyable chewingtime can be prolonged by prolonging the time during which at least 15%of the original flavor intensity is apparent.

In order to preserve the initial flavor burst and maximize the efficientuse of the flavor ingredients, it is desirable that as much of the fruitflavor as possible be in the free (unencapsulated) form. Therefore,there is a considerable demand for a technique for enhancing thelong-term detectability of fruit flavors without relying significantlyon conventional encapsulation techniques.

SUMMARY OF THE INVENTION

The present invention is a method of making an improved gum base which,when incorporated into a free fruit-flavored chewing gum, will cause thegum to have enhanced long-term fruit flavor intensity without relyingsignificantly on flavor encapsulation techniques. By using the gum baseprepared according to the invention, the chewing gum will maintain theintegrity of the initial flavor burst using free (unencapsulated)flavors, while at the same time changing the rate of free fruit flavordissipation so that the chewing gum maintains at least 15% of itsoriginal detectable flavor intensity over a longer period of time. As aresult, the consumer experiences a prolonged period of chewingenjoyment.

Generally, the invention will prolong the period of chewing enjoyment byat least one minute, and more often by two or more minutes, compared tofruit-flavored chewing gums equipped with conventionally prepared gumbases. This means that the period of chewing enjoyment, during which thedetectable fruit flavor remains at or above 15% of the original flavorintensity, can now be increased to about 10-15 minutes, compared to aprevious range of 8-12 minutes, without increasing the amount of fruitflavor added to the chewing gum, and without lowering the intensity ofthe initial flavor burst. Still longer periods of chewing enjoyment canbe obtained by increasing the amount of free fruit flavor used with thechewing gums of the invention, without significantly affecting theinitial flavor burst.

The foregoing assumes that the fruit flavor will be in the entirely free(unencapsulated) form. Of course, the benefits of the invention can alsobe realized in chewing gums that contain some encapsulated fruit flavorprovided that there is mostly free fruit flavor present in addition tothe encapsulated fruit flavor.

The benefits of the invention can be realized by selecting andproviding, in the chewing gum base, a water-insoluble chewing gumingredient which has a Solubility Parameter within ±2.0 S.P.U.'s of theSolubility Parameter of the free fruit flavor ingredient in the gumwhose long term flavor is being enhanced. For added benefit, theSolubility Parameter of the water-insoluble ingredient should preferablybe within ±1.0 S.P.U. of the Solubility Parameter of the free fruitflavor ingredient whose long term flavor is being enhanced. The selectedwater-insoluble ingredient acts as a restrainer for the free flavoringredients, slowing its release without encapsulating it.

The selected water-insoluble ingredient should be added to the gum basein an amount sufficient to constitute at least 7% by weight of theentire chewing gum composition, or at least four times the weightpercentage of the free flavor ingredient whose flavor is being enhanced,whichever is greater. Preferably, the selected water-insolubleingredient will be added to the base in an amount sufficient toconstitute at least five times the weight percentage of the free fruitflavor ingredient whose long term flavor is being enhanced.

When selecting the water-insoluble ingredient, it is important toconsider not only the chemical nature of the ingredient, but also itsmolecular weight. When more than one free fruit flavor ingredient is tobe used in the gum, it is important to consider individually theSolubility Parameter of each fruit flavor for which enhancement isdesired. If the different fruit flavors have Solubility Parameters thatare close together, then it may be possible to enhance the longetivityof more than one fruit flavor using the same water-insoluble ingredientin the gum base. On the other hand, if the different fruit flavors haveSolubility Parameters which are far apart, then it may be necessary touse more than one properly selected water-insoluble ingredient in thebase to provide long-term enhancement of the different fruit flavors inthe gum.

With the foregoing in mind, it is a feature and advantage of theinvention to provide a method of preparing a gum base, and a gum basemade thereby, which causes a fruit-flavored chewing gum to have apleasant chewing life at least one minute longer, and often two or moreminutes longer, than the pleasant chewing life of a conventionalfruit-flavored chewing gum containing the same level of free fruitflavor and a conventionally-made gum base.

It is also a feature and advantage of the invention to provide a methodof making a gum base, and a gum base made thereby, for use in afruit-flavored chewing gum, which maximizes the efficient use of freefruit flavor by enhancing the long-term flavor intensity withoutsacrificing the initial flavor burst.

It is also a feature and advantage of the invention to provide thechewing gum manufacturer with physiochemical characteristics, andrelationships based on these characteristics, which permit plannedpreformulation of gum bases for use in free fruit-flavored chewing gums,which facilitate both an initial burst of flavor and enhanced long-termflavor release.

It is also a feature and advantage of the invention to coordinate theuse of a calculated Solubility Parameter for at least one, and possiblya mixture, of free fruit flavor ingredients in chewing gum with at leastone selected water-insoluble chewing gum ingredient in a gum base so asto provide the manufacturer the option of predictably formulating a gumbase for a free fruit-flavored chewing gum which facilitates both aninitial burst of flavor and a pleasant longer-lasting chewing life.

The foregoing and other features and advantages of the invention willbecome further apparent from the following detailed description of thepresently preferred embodiments, read in conjunction with theaccompanying examples and drawings. The detailed description, examplesand drawings are merely illustrative rather than limiting, with thescope of the invention being defined by the appended claims andequivalents thereof.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the fruit flavor intensity as a function of chewing timefor a conventional fruit-flavored chewing gum versus a fruit-flavoredchewing gum using a gum base prepared according to of the invention,using equal starting levels of free fruit flavor. FIG. 1 corresponds tothe samples described in Examples 9 and 13.

FIG. 2 shows the fruit flavor quality as a function of time for aconventional fruit-flavored chewing gum versus a fruit-flavored chewinggum using a gum base prepared according to the invention, as describedin Examples 9 and 13.

FIG. 3 shows the fruit flavor intensity as a function of time for aconventional fruit-flavored chewing gum versus a fruit-flavored chewinggum using a gum base prepared according to the invention, wherein thegum incorporating the invention contains a higher level of free fruitflavor to compensate for the longer period of desired enhanced flavorrelease. FIG. 3 corresponds to the samples described in Examples 10 and14.

FIG. 4 shows the fruit flavor quality as a function of time for aconventional fruit-flavored chewing gum versus a fruit-flavored chewinggum using a gum base prepared according to the invention, as describedin Examples 10 and 14.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Different materials or ingredients having the same or similar SolubilityParameters have an increased tendency to become attracted to and/ormixed with each other. The present invention makes use of this fact byproviding, in the chewing gum base, at least 7% by weight of the chewinggum of a water-insoluble ingredient having the same or similarSolubility Parameter as the free fruit flavoring agent whose long-termflavor is being enhanced. By attracting or attaching molecules of afruit flavoring agent to the selected water-insoluble ingredient, thefree fruit flavoring agent acquires a tendency to dissipate or releasemore slowly and over a longer period of time. Surprisingly, this isaccomplished without compromising any of the initial flavor burst whichis desirably associated with fruit-flavored chewing gum.

As explained in the above-identified publication by Dr. Billmeyerentitled "Textbook of Polymer Science", the easiest way to calculate theSolubility Parameter for an ingredient is to use the molar attractionconstants E presented in Table 1 below:

                  TABLE 1                                                         ______________________________________                                        Molar Attraction Constants E                                                  (Dimensions = (J · m.sup.3).sup.1/2  × 10.sup.-3 /mole)        Group (i)   E.sub.i   Group (i)    E.sub.i.sup.-                              ______________________________________                                        CH.sub.3    301.5     --NH.sub.2   463.8                                      --CH.sub.2 --                                                                             269       --NH--       368.5                                      >CH--       176       --N--        125                                        >C<         65.9      --C.tbd.N    725-8                                      CH.sub.2 ═                                                                            259       NCO          734                                        --CH═   244       --S--        429                                        >C═     173       Cl.sub.2     701                                        --CH═aromatic                                                                         240       Cl primary   420                                        --C═aromatic                                                                          200       Cl secondary 426                                        --O-ether, acetal                                                                         235       Cl aromatic  329.5                                      --O-epoxide 361       F            84.6                                       --COO--     668.5     Conjugation  47.6                                       >C═O    538       cis          -14.6                                      --CHO       599       trans        -27.6                                      (CO).sub.2 O                                                                              1161      6-Membered ring                                                                            48                                         --OH        462.6     ortho        14.8                                       OH aromatic 350       meta         13.5                                       --H acidic dimer                                                                          -103.4    para         82.5                                       ______________________________________                                    

In the above table, which is derived from the Billmeyer publicationreferenced above and converted to the indicated dimensions, certainvalues of E for particular chemical moieties are presented. Whencalculating the Solubility Parameter for a particular chewing gum or gumbase ingredient such as, for example, a water-insoluble ingredient, allof the moieties contained in the ingredient are summed over themolecular configuration of that ingredient, or of the repeating unit ifthe ingredient is a polymer. The summation is then multiplied by thedensity of the ingredient and divided by its molecular weight (repeatingunit molecular weight for polymers), to yield the Solubility Parameter.

Before selecting the specific water-insoluble ingredient to be used, theSolubility Parameter of the free flavoring agent whose long-term flavoris being enhanced, must be known or determined. The following Table 2provides the Solubility Parameters for a large number of free fruitflavoring agents.

                  TABLE 2                                                         ______________________________________                                        Solubility Parameters for Free                                                Fruit Flavoring Agents                                                        Fruit Flavor      δ (S.P.U.)                                            ______________________________________                                        lemon oil (limonene)                                                                            15.3                                                        orange oil (limonene)                                                                           15.3                                                        ethyl butyrate    17.4                                                        amyl acetate      17.4                                                        ethyl propionate  17.2                                                        ethyl acetate     18.6                                                        ethyl alcohol     26.0                                                        ethyl caproate    17.2                                                        methyl salicylate 21.7                                                        eugenol           19.3                                                        benzaldehyde      19.2                                                        cinnamic aldehyde 20.5                                                        l-carvone         17.6                                                        isoamyl acetate   16.0                                                        isobutyl acetate  17.0                                                        methyl acetate    19.5                                                        ______________________________________                                    

The next step is to select a water-insoluble ingredient, i.e., aningredient that will not dissolve during chewing, yet which has aSolubility Parameter as close as possible to that of the free flavoringagent. The selected water-insoluble ingredient, which serves as a"restrainer" for the free fruit flavoring agent in the chewing gum, maybe a properly selected conventional chewing gum base ingredient (e.g. anelastomer) or an unconventional chewing gum base ingredient. Properlyselected polymers are especially useful as restrainers of free fruitflavors because they do not dissolve in the mouth during chewing. Thefollowing Table 3 lists the Solubility Parameters for many conventionalwater-insoluble chewing gum base ingredients.

                  TABLE 3                                                         ______________________________________                                        Solubility Parameters for Water-Insoluble                                     Chewing Gum Base Ingredients                                                  Ingredient                δ (S.P.U.'s)                                  ______________________________________                                        Waxes                                                                         Microcrystalline wax, m.p. = 180° F.                                                             17.5                                                Microcrystalline wax, m.p. = 170° F.                                                             17.3                                                Paraffin wax              17.5                                                White paraffin wax, m.p. = 145° F.                                                               17.3                                                White paraffin wax, m.p. = 135° F.                                                               17.1                                                Synthetic Elastomer                                                           98.5% isobutylene-1.5% isoprene,                                                                        16.0                                                mol. wt. = 120,000-150,000                                                                              16.0                                                Polyisobutylene, mol. wt. = 50,000-80,000                                     75% butadiene (molar)/25% styrene (molar)                                                               17.0                                                copolymer, mol. wt. = 80,000-100,000                                          50% butydiene (molar)/50% styrene (molar)                                                               17.0                                                copolymer                                                                     Natural Elastomers                                                            Jelutong                  17.0                                                Massarandula balatu       17.0                                                Sorva                     17.0                                                Resins                                                                        Glycerol ester of polymerized rosin                                                                     18.2                                                Glycerol ester of hydrogenated rosin                                                                    18.2                                                Glycerol ester of wood rosin                                                                            18.5                                                Plasticizers                                                                  Glycerol monostearate     19.0                                                Glycerol triacetate       19.3                                                Fats, Oils                                                                    Hydrogenated cottonseed oil                                                                             18.3                                                Hydrogenated soybean oil  18.8                                                Partially hydrogenated vegetable oil                                                                    21.0                                                Vinyl Polymers                                                                Polyvinyl acetate (mol. wt. = 25,000)                                                                   19.1                                                Polyvinyl acetate (mol. wt. = 50,000-80,000)                                                            18.9                                                ______________________________________                                    

In order to effectively enhance the long-term flavor, the selectedrestrainer must have a Solubility Parameter within ±2.0 S.P.U.'s of theSolubility Parameter of the free fruit flavoring agent being enhanced.The Solubility Parameter of the restrainer will preferably be within±1.0 S.P.U. of that of the free fruit flavoring agent, most preferablywithin ±0.5 S.P.U.'s of that of the free fruit flavoring agent.

The effectiveness of the restrainer for providing long-term flavorenhancement increases with the amount of restrainer used in the gumbase, with the amount of gum base used in the chewing gum, and with themolecular weight of the restrainer. In order to meet the objectives ofthe invention, the selected restrainer should constitute at least 7% byweight of the entire chewing gum composition, preferably at least 9% byweight of the entire chewing gum composition, most preferably at least11% by weight of the entire chewing gum composition.

The amount of restrainer required in the gum base is also dependent onthe amount of free fruit flavor in the gum whose long-term intensity isbeing enhanced. In order to meet the objectives of the invention, theselected restrainer should be present, in the chewing gum, in at leastfour times the weight percentage of the free flavor ingredient whoselong term flavor is being enhanced, preferably at least five times theweight percentage of the free fruit flavor, most preferably at least sixtimes the weight percentage of the free fruit flavor.

Therefore, the amount of restrainer that needs to be added to thechewing gum base varies depending on the amount of gum base used in thefree fruit-flavored gum, and on the amount of free fruit flavor in thegum. For most free fruit-flavored chewing gum applications, the gum baseconstitutes about 10-50% by weight of the Chewing gum. In theseapplications, the restrainer should generally constitute about 20-75% byweight of the gum base, more commonly about 25-55% by weight of the gumbase, most commonly about 30-40% by weight of the gum base.

As stated above, the invention gum base is useful for the purpose ofenhancing the long-term intensity of free fruit flavor in chewing gumwithout relying on encapsulating techniques and without significantlyaffecting the intensity of the initial flavor burst. Therefore, it ismost preferred that the gum base be used in fruit-flavored chewing gumthat is substantially devoid of encapsulated fruit flavor, or at leastwherein less than about 1.0% by weight encapsulated fruit flavor ispresent. In situations where the presence of encapsulated fruit flavoris desired for one reason or another, the amount of free fruit flavorshould exceed the amount of fruit flavor that has been encapsulated,preferably by a weight ratio of at least 2:1.

In order to achieve the benefit of enhanced long-term flavor intensitywithout sacrificing the initial flavor burst, it is not necessary toincrease the amount of free fruit flavor in the chewing gum above thelevel that would be present in conventional fruit-flavored gums.However, a surprising benefit arises when the amount of free fruitflavor in a chewing gum containing the inventive gum base is raisedabove conventional levels. It has been discovered that the free fruitflavor level can be increased significantly above conventional levels ingums containing the inventive base without raising the initial flavorburst to excessive levels, so that an increase in flavor intensity isobserved at all times during the chew except the initial burst.

In other words, a significant increase the free fruit flavor levels inconventional chewing gums often had the undesirable effect of raisingthe initial flavor burst to excessive intensity, without solving theproblem of rapid flavor dissipation. Also, high free fruit flavor levelstend to soften the gum excessively, causing the gum to be too softduring chewing. When the gum base of the invention is used, on the otherhand, the level of free fruit flavor can be significantly increasedabove conventional levels without significantly affecting the intensityof the initial flavor burst, and without significantly softening thegum, while greatly enhancing the flavor intensity later in the chew viaslower flavor dissipation.

Accordingly, the chewing gum containing the inventive gum base cangenerality include anywhere between about 0.3-10.0% by weight of free(not encapsulated) fruit flavoring agent. Preferably, the level of freefruit flavoring agent is about 1.0-6.0% by weight of the chewing gum,most preferably about 1.5-4.0% by weight of the chewing gum.

The amount of free fruit flavor desired will vary depending on the typeof fruit flavor employed. Any free fruit flavor can be used with thechewing gum of the invention, including any of the fruit flavors listedin Table 2.

The selected water-insoluble restrainer is preferably a polymer whichhas a Solubility Parameter as close as possible to that of the freefruit flavor being enhanced. The restrainer is added during manufactureof the gum base and, included as part of the base, in accordance withthis invention. It is important that the restrainer be well dispersed inthe gum base and, ultimately, in the chewing gum in order to come intocontact with, and restrain, as much of the free fruit flavoring agent aspossible. Therefore, if the restrainer is difficult to disperse, it ispreferable to add the restrainer as early as possible during manufactureof the gum base, at or near the start of the mixing cycle, in order toensure its maximum ultimate dispersion in the chewing gum.Advantageously, the majority or all of the restrainer should be addedwithin the first 25% of the total mixing cycle time, preferably withinthe first 10% of the total mixing cycle time, most preferably at thestart of the mixing cycle.

Medium to high molecular weight polyvinyl acetates (M.W.=30,000-80,000)are examples of restrainers that should be added as early as possible inthe gum base mixing cycle, in order to obtain their thorough dispersionand achieve the maximum long-term flavor enhancement in the gum. Becauseof their desirable Solubility Parameter of around 19, the polyvinylacetates act as excellent restrainers for a large number of free fruitflavor ingredients. It has also been learned that polyvinyl acetatesperform better as a restrainer when little or no gum base plasticizer ispresent in the gum base or chewing gum. It is believed that gum baseplasticizers, for example, glycerol triacetate, tend to soften polyvinylacetate and reduce its flavor restraining effect. Therefore, the chewinggum base preferably contains no more than about 4.0% by weight gum baseplasticizer, more preferably no more than about 2.0% by weight gum baseplasticizer, and is most preferably substantially free of gum baseplasticizer, when polyvinyl acetate is used.

Another reason to select polyvinyl acetate as the restrainer is becauseof its compatibility with fruit flavor esters. It is believed thatesters, like acetates, are very compatible with polyvinyl acetatebecause of their similar chemical structures. Therefore, polyvinylacetate is the most preferred restrainer for use in gum base and for afruit flavored gum product. Fruit flavors are readily absorbed(especially acetates) in polyvinyl acetate and act as a plasticizer forpolyvinyl acetate.

Once a polymer restrainer has been properly selected based on itsSolubility Parameter, there are a variety of ways to optimize its longterm flavor enhancing performance. As explained above, the flavorenhancement generally increases with increasing amount of restrainer inthe chewing gum. Because the restrainer is formulated as part of the gumbase, the flavor enhancement effect will increase with increasing gumbase levels in the chewing gum.

Another technique for increasing the effectiveness of the restrainer isto increase its molecular weight. While not intending to be bound bytheory, it is believed that higher molecular weight polymers offer agreater hindrance to immediate penetration by water during chewing.Therefore, when a fruit flavoring molecule becomes attached or attractedto a restrainer of higher molecular weight, the flavor molecule is lesslikely to be immediately exposed to water during chewing. As the gum ischewed, the longer restrainer molecule is caused to twist and turn asthe flavor molecules attached at various locations along the polymerchain are gradually released.

Any ingredient which loosens, softens or plasticizes the restrainer maywork against the invention by providing quicker exposure of the flavormolecules to water during chewing. Therefore, as explained above, it isdesirable to minimize the amount of conventional plasticizers present inthe chewing gum base of the invention. For similar reasons, it isdesirable to minimize the level of wax in the gum base. Preferably,waxes will constitute no more than about 2.0% by weight of the gum baseprepared according to the invention. The gum base will most preferablybe substantially devoid of waxes, especially petroleum waxes. Higherlevels of free flavor can be added to normalize the chewing gum texture.

Chewing gum prepared using the gum base of the invention will generallyinclude a water soluble bulk portion, the generally water insolublechewing gum base including the water insoluble restrainer, and one ormore free fruit flavoring agents. The water soluble bulk portion andflavoring agents dissipate over a period of time during chewing. The gumbase, including the restrainer, is retained in the mouth throughout thechewing process.

In addition to the restrainer, the generally water-insoluble gum basemay include elastomers, resins, fillers, and a minimum of fats, oils,waxes and softeners. The elastomers may include polyisobutylene,isobutylene-isoprene copolymer, styrene butadiene rubber and naturallatexes such as chicle. The resins may include polyvinyl acetate,terpene resins, and rosin esters. Medium to high molecular weightpolyvinyl acetate (M.W.=30,000-80,000) is a preferred resin, with amolecular weight of 40,000-50,000 being most preferred. Fats and oilsmay include animal fats such as lard and tallow, vegetable oils such assoybean and cottonseed oils, hydrogenated and partially hydrogenatedvegetable oils, and cocoa butter. Commonly used waxes include petroleumwaxes such as paraffin and microcrystalline wax, natural waxes such asbeeswax, candellia, carnauba and polyethylene wax.

The gum base typically also includes a filler component such as calciumcarbonate, magnesium carbonate, talc, dicalcium phosphate and the like;gum base softeners, including glycerol monostearate and lecithin; andoptional ingredients such as antioxidants, colors and emulsifiers. Inaccordance with the invention, gum base plasticizers (softeners) shouldbe kept to a minimum or eliminated when, as with polyvinyl acetate, theymay hinder the performance of the restrainer. The gum base constitutesbetween 5-95% by weight of the chewing gum composition, more typically10-50% by weight of the chewing gum, and most commonly 20-30% by weightof the chewing gum. Because the restrainer is included in the gum base,the gum base must be present in an amount sufficient to ensure that therestrainer constitutes at least about 7% by weight of the chewing gum orfour times the weight percentage of the free fruit flavor beingenhanced, as explained above.

The water soluble portion of the chewing gum may include chewing gumsofteners, bulk sweeteners, high intensity sweeteners, fruit flavoringagents and combinations thereof. When used, the softeners generallyconstitute between about 0.5-15% by weight of the chewing gum. Thechewing gum softeners may include glycerin, lecithin, and combinationsthereof. Aqueous sweetener solutions such as those containing sorbitol,hydrogenated starch hydrolysates, corn syrup and combinations thereof,may also be used as softeners and binding agents in chewing gum.

Bulk sweeteners constitute between 5-95% by weight of the chewing gum,more typically 20-80% by weight of the chewing gum and most commonly30-60% by weight of the chewing gum. Bulk sweeteners may include bothsugar and sugarless sweeteners and components. Sugar sweeteners mayinclude saccharide containing components including but not limited tosucrose, dextrose, maltose, dextrin, dried invert sugar, fructose,levulose, galactose, corn syrup solids, and the like, alone or incombination. Sugarless sweeteners include components with sweeteningcharacteristics but are devoid of the commonly known sugars. Sugarlesssweeteners include but are not limited to sugar alcohols such assorbitol, mannitol, xylitol, hydrogenated starch hydrolysates, maltitol,and the like, alone or in combination.

High intensity sweeteners may also be present and are commonly used withsugarless sweeteners. When used, high intensity sweeteners typicallyconstitute between 0.001-5% by weight of the chewing gum, preferablybetween 0.01-1% by weight of the chewing gum. Typically, high intensitysweeteners are at least 20 times sweeter than sucrose. These may includebut are not limited to sucralose, aspartame, salts of acesulfame,alitame, saccharin and its salts, cyclamic acid and its salts,glycyrrhizin, dihydrochalcones, thaumatin, monellin, and the like, aloneor in combination.

Combinations of sugar and/or sugarless sweeteners may be used in chewinggum. The sweetener may also function in the chewing gum in whole or inpart as a water soluble bulking agent. Additionally, the softener mayprovide additional sweetness such as with aqueous sugar or alditolsolutions.

Free fruit flavor should generally be present in the chewing gum in anamount within the range of about 0.3-10.0% by weight of the chewing gum,preferably between about 1.0-6.0% by weight of the chewing gum, mostpreferably between about 1.5-4.0% by weight of the chewing gum. Freefruit flavoring agents may include any of the ingredients listed inTable 2, or any other fruit flavoring agent. Additional (nonfruit)flavors may optionally be included such as peppermint oil, spearmintoil, other mint oils, clove oil, oil of wintergreen, anise and the like.Natural or artificial flavoring agents and components may be used in thechewing gum. Natural and artificial flavoring agents may be combined inany sensorially acceptable fashion.

Optional ingredients such as colors, emulsifiers, pharmaceutical agentsand additional flavoring agents may also be included in chewing gum.

The chewing gum is generally manufactured by sequentially adding thevarious chewing gum ingredients to any commercially available mixerknown in the art. After the ingredients have been thoroughly mixed, thegum mass is discharged from the mixer and shaped into the desired formsuch as by rolling into sheets, scoring and cutting into sticks.Generally, the ingredients are mixed by first melting the gum base andadding it to the running mixer. The gum base may alternatively be meltediron the mixer. Color and emulsifiers can be added at this time.

A chewing gum softener such as glycerin can be added next along withsyrup and part of the bulk portion. Further parts of the bulk portionmay then be added to the mixer. Flavoring agents are typically addedwith the final part of the bulk portion. The entire mixing processtypically takes from five to fifteen minutes, although longer mixingtimes are sometimes required. Those skilled in the art will recognizethat variations of this mixing procedure, or other mixing procedures,may be followed.

As state above, the water-insoluble restrainer is added initially intothe chewing gum base. When medium to high molecular weight polyvinylacetate is used as the restrainer, it should be added during earlymanufacture of the gum base, at or near the front of the otherwiseconventional mixing cycle, with the elastomer and filler. Once thepolyvinyl-acetate has been dispersed, the remaining gum base ingredients(emulsifiers, etc.) can be added. Typically, a sigma blade batch mixercan be used to make the gum base.

A wide range of changes and modifications to the embodiments of theinvention described above will be apparent to persons skilled in theart. The following examples are not to be construed as imposinglimitations on the invention, but are included merely to illustratepreferred embodiments.

EXAMPLE 1-(COMPARATIVE)

For comparison purposes, four gum bases were made having the followingcompositions:

    ______________________________________                                                       % BY WEIGHT  % BY WEIGHT                                                      IN GUM BASE  IN GUM BASE                                                      (EXAMPLES    (EXAMPLES                                         INGREDIENT     1 AND 3)     2 AND 4)                                          ______________________________________                                        Isobutylene-isoprene                                                                         10.1         --                                                copolymer                                                                     Polyisobutylene                                                                               1.6         12.0-7.0                                          Glycerol esters of                                                                           --           13.0                                              wood rosin                                                                    Terpene resins 26.9         --                                                High M.W. polyvinyl                                                                          --           31.3                                              acetate (mol. wt. =                                                           65,000)                                                                       Low M.W. polyvinyl                                                                           27.3         --                                                acetate (mol. wt. =                                                           25,000)                                                                       Lecithin        2.7         --                                                Glycerol monostearate                                                                         4.8          5.9                                              Triacetin      --            4.7                                              Microcrystalline/                                                                            13.3          6.5-13.0                                         paraffin wax                                                                  Hydrogenated vegetable                                                                        2.0         6.5-0                                             oil                                                                           Calcium carbonate                                                                            11.2         20.0-25.0                                         Color/BHT      0.1-0.0       0.1                                              TOTAL          100.0        100.0                                             ______________________________________                                    

As shown above, all four gum bases contained polyvinyl acetate, but alsocontained considerable amounts of waxes and plasticizers.

The base of Example 1 was made using a Haake Rheocord 90 mixer equippedwith a 3000 E mixing bowl, at 120° C. and a motor speed of 60 rpm, toproduce a 450-gram batch. The total mixing cycle was 2.5 hours. Thefollowing table shows when and how much of each gum base ingredient wasadded at different times during the mixing cycle.

    ______________________________________                                                                 TIME OF                                              INGREDIENT  % BY WEIGHT  ADDITION DURING                                      (EXAMPLE 1) ADDED        MIXING CYCLE                                         ______________________________________                                        Isobutylene-isoprene                                                                      10.1         0:00                                                 copolymer (ground)                                                            Polyisobutylene                                                                           1.6          0:00                                                 Calcium carbonate                                                                         11.2         0:00                                                 Color       0.1          0:00                                                 Terpene resin                                                                             2.96         0:00                                                 Terpene resin                                                                             2.96         0:30                                                 Terpene resin                                                                             5.92         0:40                                                 Terpene resin                                                                             7.53         0:50                                                 Terpene resin                                                                             7.53         1:00                                                 Low M.W. poly-                                                                            7.06         1:10                                                 vinyl acetate                                                                 Low M.W. poly-                                                                            10.12        1:20                                                 vinyl acetate                                                                 Low M.W. poly-                                                                            10.12        1:30                                                 vinyl acetate                                                                 Paraffin wax                                                                              6.9          2:00                                                 Lecithin    2.7          2:00                                                 Glycerol mono-                                                                            4.8          2:00                                                 stearate                                                                      Microcrystalline                                                                          6.4          2:00                                                 wax                                                                           Hydrogenated vege-                                                                        2.0          2:00                                                 table oil                                                                     TOTAL       100.0        2:30                                                 ______________________________________                                    

Note that the polyvinyl acetate was added about halfway through themixing cycle, in accordance with the conventional procedure, for thebase of Example 1. The base of Example 1 was not suitable for furthertesting, and it was determined that mixing mimes needed to be lower forthe lab mixer.

The base of Example 2 was made using a Werner-Pfleiderer productionmixer using 40 psi steam pressure, a batch temperature of 75°-80° C., adrive shaft speed of 163 rpm, and a total mixing cycle time of 1.75hours. The following table shows when and how much of each ingredientwas added at different times during the mixing cycle. Note that,although the high molecular weight polyvinyl acetate was added early, itwas treated almost immediately with a significant quantity of triacetinplasticizer.

    ______________________________________                                                                 TIME OF                                              INGREDIENT  % BY WEIGHT  ADDITION DURING                                      (EXAMPLE 2) ADDED        MIXING CYCLE                                         ______________________________________                                        High M.W. poly-                                                                           31.36        0:00                                                 vinyl acetate                                                                 Glycerin triacetate                                                                       4.7          0:05                                                 Polyisobutylene                                                                           12.0         0:20                                                 Calcium carbonate                                                                         11.5         0:20                                                 Glycerol ester of                                                                         13.0         0:35                                                 wood rosin                                                                    Calcium carbonate                                                                         8.5          0:35                                                 Paraffin wax                                                                              6.5          1:15                                                 Hydrogenated vege-                                                                        6.5          1:25                                                 table oil                                                                     Glycerol mono-                                                                            5.9          1:25                                                 stearate                                                                      BHT         0.04         1:25                                                 TOTAL       100.0        1:45                                                 ______________________________________                                    

The gum base of Example 3 (having an almost identical composition toExample 1) was made using a shortened mixing cycle on the Haake Rheocord90 mixer. The base of Example 3 was made at a temperature of 115° C., amotor speed of 60 rpm, and a total mixing cycle time of 70 minutes.After 50 minutes, the mixer was cooled to 50° C. The following tableshows when and how much of each ingredient was added at different timesduring the mixing cycle.

    ______________________________________                                                                 TIME OF                                              INGREDIENT  % BY WEIGHT  ADDITION DURING                                      (EXAMPLE 3) ADDED        MIXING CYCLE                                         ______________________________________                                        Isobutylene-isoprene                                                                      10.1         0:00                                                 copolymer (ground)                                                            Polyisobutylene                                                                           1.6          0:00                                                 Calcium carbonate                                                                         11.2         0:00                                                 Terpene resin                                                                             2.96         0:00                                                 Terpene resin                                                                             2.96         0:07                                                 Terpene resin                                                                             5.92         0:10                                                 Terpene resin                                                                             7.53         0:15                                                 Terpene resin                                                                             7.53         0:20                                                 Low M.W. poly-                                                                            7.06         0:25                                                 vinyl acetate                                                                 Low M.W. poly-                                                                            10.12        0:30                                                 vinyl acetate                                                                 Low M.W. poly-                                                                            10.12        0:35                                                 vinyl acetate                                                                 Microcrystalline                                                                          6.4          0:40                                                 wax                                                                           Paraffin wax                                                                              6.9          0:45                                                 Hydrogenated vege-                                                                        2.0          0:45                                                 table oil                                                                     Glycerol mono-                                                                            4.8          0:45                                                 stearate                                                                      Lecithin    2.7          0:50                                                 TOTAL       100.0        0:70                                                 ______________________________________                                    

Note that the order of addition of the ingredients for Example 3 wasvery similar to that of Example 1. However, the mixing time was muchshorter.

The gum base of Example 4 (similar in composition to Example 2) wasprepared using the Haake Rheocord 90 mixer at a temperature of 78° C., amotor speed of 40 rpm, and a shorter total mixing time of 45 minutes.The temperature was lowered to 65° C. after 23 minutes, and was loweredagain to 50° C. after 35 minutes. The following table shows when and howmuch of each ingredient was added at different times during the mixingcycle.

    ______________________________________                                                                   TIME OF                                                            % BY       ADDITION                                           INGREDIENT      WEIGHT     DURING                                             (EXAMPLE 4)     ADDED      MIXING CYCLE                                       ______________________________________                                        High M.W. polyvinyl acetate                                                                   31.3       0:00                                               Glycerol triacetate                                                                            4.7       0:05                                               Calcium carbonate                                                                             11.4       0:10                                               Polyisobutylene  7.0       0:15                                               Glycerol ester of wood rosin                                                                  13.0       0:17                                               Calcium carbonate                                                                             13.6       0:17                                               Paraffin wax    13.0       0:23                                               Glycerol monostearate                                                                          5.9       0:35                                               TOTAL           100.0      0:45                                               ______________________________________                                    

EXAMPLES 5-8 (INVENTIVE)

Using the method of the invention, four gum bases were made having thefollowing compositions:

    ______________________________________                                        % BY WEIGHT IN GUM BASE                                                       INGREDIENT       Ex. 5   Ex. 6   Ex. 7 Ex. 8                                  ______________________________________                                        Isobutylene-isoprene                                                                            7.0     7.0     7.0  7.0                                    copolymer                                                                     Polyisobutylene   3.0     3.0     3.0  3.0                                    Glycerol ester of wood rosin                                                                   10.0    10.0    10.0  9.9                                    Terpene resin    10.0    10.0    10.0  10.0                                   Medium M.W. polyvinyl                                                                          20.0    20.0    20.0  20.0                                   acetate                                                                       (mol. wt. = 40,000)                                                           Low M.W. polyvinyl                                                                             10.0    15.0    15.0  14.5                                   acetate                                                                       (mol. wt. = 25,000)                                                           Lecithin          5.0     5.0     5.0  5.0                                    Glycerol monostearate                                                                          10.0    10.0    10.0  10.0                                   Wax              10.0     5.0    --    --                                     Calcium carbonate                                                                              15.0    15.0    20.0  19.95                                  Color/BHT        --      --      --     0.65                                  TOTAL            100.0   100.0   100.0 100.0                                  ______________________________________                                    

As shown above, the gum bases of Examples 5, 6 and 7 had respectivelylower wax levels. Examples 6 and 7 contained more polyvinyl acetate thanExample 5. Example 7 contained more calcium carbonate than Examples 5and 6.

The gum base of Example 8 had essentially the same composition ofExample 7 except for minor changes made in order to adapt to theproduction-scale equipment used to prepare Example 8.

The gum bases of Examples 5-7 were made using a Haake Rheocord 90 mixerat a temperature of 115° C. and a motor speed of 40 rpm. The temperaturewas lowered near the end of each mixing cycle. The gum base of Example 8was made using a Werner-Pfleiderer production scale mixer using a steampressure of 45 psi, a drive speed of 252 rpm, and a mixing temperatureof 115° C. The following table indicates, for each of Examples 5-7, whenand how much of each gum base ingredient was added at different timesduring the respective mixing cycles.

    ______________________________________                                        % BY WEIGHT ADDED AND                                                         TIME OF ADDITION DURING MIXING CYCLE                                          INGREDIENT  EXAMPLE 5  EXAMPLE 6  EXAMPLE 7                                   ______________________________________                                        Color       --      --     --    --   --    --                                Medium M.W. 20.0    0:00   20.0  0:00 20.0  0:00                              polyvinyl acetate                                                             Isobutylene-                                                                              7.0     0:00   7.0   0:00 7.0   0:00                              isoprene copolymer                                                            Calcium carbonate                                                                         15.0    0:00   15.0  0:00 20.0  0:00                              Terpene resin                                                                             5.0     0:00   5.0   0:00 5.0   0:00                              Terpene resin                                                                             5.0     0:05   5.0   0:05 5.0   0:05                              Low M.W.    10.0    0:05   15.0  0:05 15.0  0:05                              polyvinyl acetate                                                             Glycerol ester of                                                                         5.0     0:08   5.0   0:08 5.0   0:08                              wood resin                                                                    Glycerol ester of                                                                         5.0     0:10   5.0   0:10 5.0   0:10                              wood resin                                                                    Polyisobutylene                                                                           3.0     0:13   3.0   0:13 3.0   0:13                              Wax         10.0    0:20   5.0   0:20 --    --                                BHT         --      --     --    --   --    --                                Glycerol    10.0    0:23   10.0  0:23 10.0  0:23                              monostearate                                                                  Lecithin    5.0     0:30   5.0   0:30 5.0   0:30                              TOTAL       100.0   0:32   100.0 0:32 100.0 0:32                              ______________________________________                                    

The following table indicates, for Example 8, when and how much of eachgum base ingredient was added at different times during the mixingcycle.

    ______________________________________                                                                   TIME OF                                                           % BY        ADDITION                                                          WEIGHT      DURING                                             INGREDIENT     (EXAMPLE 8) MIXING CYCLE                                       ______________________________________                                        Color          0.6         0:00                                               Calcium carbonate                                                                            19.95       0:00                                               Isobutylene-   7.0         0:00                                               isoprene copolymer                                                            Glycerol-ester of                                                                            4.3         0:00                                               wood rosin                                                                    Polyisobutylene                                                                              3.0         0:00                                               Terpene resin  5.0         0:30                                               Medium M.W.    10.0        0:45                                               polyvinyl acetate                                                             Medium M.W.    10.0        0:55                                               polyvinyl acetate                                                             Terpene resin  5.0         1:05                                               Low M.W.       14.5        1:15                                               polyvinyl acetate                                                             Glycerol ester of                                                                            5.6         1:25                                               wood rosin                                                                    BHT            0.05        1:40                                               Glycerol       10.0        1:40                                               monostearite                                                                  Lecithin       5.0         1:40                                               TOTAL          100.0       2:00                                               ______________________________________                                    

Note that, except for Example 8, the polyvinyl acetate was added earlyin the mixing procedure, in accordance with a preferred embodiment ofthe invention. In Example 8, the overall mixing time was much longer,allowing the polyvinyl acetate to be added at about the middle of themixing cycle. Also, the glycerol triacetate used in Examples 1-4 waseliminated from Examples 5-8.

MIXED FRUIT FLAVOR USED FOR EXAMPLES 9-14

A fruit flavor may contain a mixture of esters, lemon and orange oils,as well as aldehydes and spice materials. The mixed fruit flavor used inall the following examples 9-14 includes the following components withSolubility Parameters:

    ______________________________________                                                            %     δ (S.P.U.)                                    ______________________________________                                        Esters (ethyl butyrate, amyl                                                                        68.0    18.0                                            acetate, ethyl propionate,                                                    ethyl acetate, ethyl caproate,                                                methyl salicylate)                                                            Lemon and orange oil (limonene)                                                                     26.5    15.3                                            Spices (Eugenol and cinnamic                                                                        5.5     19.6                                            aldehyde)                                                                     Mixed fruit flavor    100.0   15.3-19.6                                       ______________________________________                                    

As can be seen from the mixed fruit flavor, the esters and spices havehigher Solubility Parameters than the lemon and orange oil. The estersand spices have similar Solubility Parameters to polyvinyl acetate andthe plasticizers. This suggests that the plasticizers and polyvinylacetate may act as restrainers for these types of:flavors, withpolyvinyl acetate being most preferred, since the amount of plasticizersshould be limited.

Also, the lemon and orange oils, whose principle component is limonene,have Solubility Parameters similar to the isobutylene-isoprene copolymerand polyisobutylene. Thus these elastomer materials would act asexcellent restrainers for these types of fruit flavors. When a mixedfruit flavor is used as above, a combination of restrainers may beneeded to give the flavor proper release characteristics to maintain thesame quality flavor throughout.

EXAMPLES 9-14 (EVALUATION)

A conventional gum base similar to Example 1 except production scale wasmade into chewing gums having the following formulations (Examples 9,10).

    ______________________________________                                        CHEWING GUM     % BY WEIGHT                                                   INGREDIENT      EXAMPLE 9   EXAMPLE 10                                        ______________________________________                                        Base similar to Example 1                                                                     24.0        19.00                                             (production scale)                                                            Glycerin        1.15        1.15                                              Glucose syrup   7.30        13.91                                             Lecthin         0.13        0.13                                              Sugar           58.14       57.72                                             Dextrose monohydrate                                                                          7.28        7.28                                              Free Mixed Fruit Flavor                                                                       2.00        0.81                                              TOTAL           100.0       100.0                                             ______________________________________                                    

The inventive gum bases of Examples 5-8 were also made into chewing gumshaving the following formulations (Examples 11-14).

    ______________________________________                                                   % BY WEIGHT                                                                     EX-      EX-      EX-    EX-                                     CHEWING      AMPLE    AMPLE    AMPLE  AMPLE                                   GUM INGREDIENT                                                                             11       12       13     14                                      ______________________________________                                        Gum base     24.00    --       --     --                                      (Example 5)                                                                   Gum base     --       24.00    --     --                                      (Example 6)                                                                   Gum base     --       --       24.00  --                                      (Example 7)                                                                   Gum base     --       --       --     24.00                                   (Example 8)                                                                   Glycerin     1.15     1.15     1.15   1.15                                    Glucose syrup                                                                              7.30     7.30     7.30   7.30                                    Lecithin     0.13     0.13     0.13   --                                      Sugar        58.14    58.14    58.14  57.82                                   Dextrose monohydrate                                                                       7.28     7.28     7.28   7.28                                    Free Mixed Fruit                                                                           2.00     2.00     2.00   2.00                                    Flavor                                                                        20% Active   --       --       --     0.45                                    encapsulated                                                                  aspartame                                                                     TOTAL        100.0    100.0    100.0  100.0                                   ______________________________________                                    

All Of the above chewing gums were evaluated by a trained 10-membersensory panel over a 20-minute chewing period. The chewing gums madefrom the inventive gum bases (Examples 11-14) exhibited prolongedperiods of enhanced flavor intensity and quality compared to both of thechewing gums made from the conventional gum bases (Examples 9 and 10).

The free mixed fruit-flavored chewing gum of Example 9 (made using theconventional base) was evaluated for fruit flavor intensity as afunction of time by the panel of sensory experts. The panelistsevaluated the gum at different chewing times on a scale between zero and15, wherein zero means no flavor intensity and 15 means very strongflavor intensity.

The results of the evaluation are shown in FIG. 1. As shown, theconventional chewing gum exhibited an initial flavor burst duringchewing of 11.7-12.1 flavor intensity units (FIU's). The flavorintensity then dissipated steadily, falling below 15% of its originallevel (or 1.8 FIU's) after about eleven minutes of chewing. In otherwords, the conventional fruit-flavored gum of Example 9 had a pleasantchewing life of about 11 minutes.

The same panelists also evaluated the flavor quality on a scale of 0-15,with higher ratings indicating better flavor quality. The results ofthis evaluation are plotted in FIG. 2. As shown, the perceived flavorquality also dissipated with chewing time, although not as fast as theflavor intensity. Nevertheless, a comparison of FIGS. 1 and 2 indicatesthat higher perceived flavor quality generally correlates with higherlevels of flavor intensity. This shows that higher flavor intensity isgenerally considered more desirable or pleasing, at least up to thelevel of the initial flavor burst.

The enhanced free fruit flavored gum of Example 13 (made using theinventive gum base of Example 7) was evaluated by the same panel forcomparison with the gum of Example 9. The results of this evaluation arealso shown in FIG. 1. As shown, the inventive chewing gum exhibited aninitial flavor burst of almost identical intensity to the flavor burstachieved with the conventional gum of Example 9. However, the flavorintensity of Example 13 dissipated at a different rate, and did not fallbelow 15% of its initial intensity level (about 1.8 F.I.U.'s) untilabout 13 minutes of chewing. In other words, the inventivefruit-flavored gum of Example 13, made with the inventive base, had apleasant chewing life about two minutes longer than that of theconventional fruit-flavored gum of Example 9.

Note that the inventive chewing gum of Example 13 contained a total of8.4% by weight polyvinyl acetate restrainer. In accordance with theinvention, and unlike the gum of Example 9, this is more than four timesthe level of free fruit flavoring agent in the chewing gum and is alsohigher than the minimum level of 7% restrainer.

As shown in FIG. 1, the inventive gum of Example 13 actually exhibited alower flavor intensity than the conventional gum of Example 9 atintermediate chewing times of from 1 to 8 minutes. This is notconsidered a drawback to the invention because, as shown below withrespect to Examples 10 and 14, the intermediate and long-term flavorintensity of chewing gum made with the inventive gum base can be greatlyenhanced without increasing the initial flavor burst, by simply addingmore free fruit flavor to the gum.

The conventional free fruit-flavored gum of Example 10 was evaluated forfruit flavor intensity as a function of time in the same manner. Asshown in FIG. 3, the conventional gum of Example 10 exhibited an initialflavor burst of 9.8-11.0 F.I.U.'s when chewing was commenced.Thereafter, the flavor intensity dissipated steadily, falling below 15%of its original value (about 1.6 F.I.U.'s) after about nine minutes ofchewing. In other words, the conventional fruit-flavored gum of Example10 had a pleasant chewing life of about nine minutes.

The same panelists also evaluated the flavor quality. The results ofthis evaluation are shown in FIG. 4. As shown, the perceived flavorquality also dissipated with time, again indicating that higherperceived flavor quality generally correlates with higher perceivedflavor intensity.

The enhanced fruit flavored gum of Example 14 (made using the inventivegum base of Example 8) was evaluated for comparison with Example 10.Note that the gum of Example 14 contained a higher level of free fruitflavor than the conventional gum of Example 10. Also, the inventive gumof Example 14 contained a total of 8.3% by weight polyvinyl acetaterestrainer supplied by the gum base. In accordance with the invention,this is more than four times the level of free fruit flavor in the gumand is also higher than the minimum level of 7% restrainer.

The results of the comparison are plotted in FIG. 3. As shown, theinventive gum of Example 14 surprisingly had an initial flavor burstabout equal to that of Example 10 even though the amount of freeflavoring agent was more than doubled. Thereafter, the gum of Example 14exhibited much higher flavor intensity than the gum of Example 10throughout the entire twenty minutes of chewing. In fact, the gum ofExample 4 never approached or fell below 15% of its original flavorintensity during the twenty minutes of chewing.

The foregoing illustrates that the inventive chewing gums of theinvention can utilize higher than normal flavor levels in an extremelybeneficial fashion, by enhancing medium and long-term flavor intensitywithout exaggerating the intensity of the initial flavor burst.

It should be appreciated that the products of the present invention arecapable of being exhibited in the form of a variety of embodiments, onlya few of which have been illustrated and described above. The inventionmay be embodied in other forms without departing from its spirit oressential characteristics. It will be appreciated that the addition ofsome other ingredients, process steps, materials or components notspecifically included may have an adverse impact on the presentinvention. The best mode of the invention may therefore excludeingredients, process steps, materials or components other than thoselisted above for inclusion or use in the invention. However, thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive, and the scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

We claim:
 1. A method of making a gum base for use in a freefruit-flavored chewing gum, the chewing gum including a free fruitflavor ingredient having a cohesive energy density and a solubilityparameter defined as the square root of the cohesive energy density, themethod comprising the steps of:providing a polymer restrainer having asolubility parameter within ±2.0 S.P.U.'s of the solubility parameter ofthe free fruit flavor ingredient, the solubility parameter of therestrainer defined as: ##EQU2## adding the restrainer into a chewing gumbase mixing cycle in an amount sufficient to constitute at least about7% by weight of the chewing gum to be made from the gum base; andblending the restrainer together with at least a filler and an elastomerto form a chewing gum base.
 2. The method of claim 1, wherein a majorityof the restrainer is added during the first 25% of the chewing gum basemixing cycle.
 3. The method of claim 1, wherein a majority of therestrainer is added during the first 10% of the chewing gum base mixingcycle.
 4. The method of claim 1, wherein a majority of the restrainer isadded at the start of the chewing gum base mixing cycle.
 5. The methodof claim 1, wherein the restrainer comprises medium to high molecularweight polyvinyl acetate.
 6. The method of claim 1, wherein therestrainer comprises low molecular weight polyvinyl acetate.
 7. Themethod of claim 1, wherein the restrainer comprises a mixture of lowmolecular weight polyvinyl acetate and medium to high molecular weightpolyvinyl acetate.
 8. The method of claim 1, wherein the chewing gumbase comprises less than about 4.0% by weight gum base plasticizer, ifany.
 9. The method of claim 1, wherein the chewing gum base comprisesless than about 4.0% by weight glycerol triacetate, if any.
 10. Themethod of claim 1, wherein the gum base comprises less than about 2.0%by weight wax.
 11. The method of claim 1, wherein the gum base issubstantially free of petroleum wax.
 12. The method of claim 1, whereinthe restrainer has a solubility parameter within about ±1.0 S.P.U.'s ofthe solubility parameter of the free fruit flavor ingredient.
 13. Themethod of claim 1, wherein the restrainer has a solubility parameterwithin about ±0.5 S.P.U.'s of the solubility parameter of the free fruitflavor ingredient.
 14. A method of making a gum base for use in a freefruit-flavored chewing gum, the chewing gum including a free fruitflavor ingredient having a cohesive energy density and a solubilityparameter defined as the square root of the cohesive energy density, themethod comprising the steps of:selecting a water-insoluble restrainerhaving a solubility parameter within ±2.0 S.P.U.'s of the solubilityparameter of the free fruit flavor ingredient, the solubility parameterof the restrainer defined as: ##EQU3## adding the restrainer into achewing gum base mixing cycle in an amount sufficient to constitute atleast four times the weight percentage of the free fruit flavoringredient to be included in the chewing gum made from the gum base; andblending the restrainer together with at least a filler and a resin toform a chewing gum base.
 15. The method of claim 14, wherein a majorityof the restrainer is added during the first 25% of the chewing gum basemixing cycle.
 16. The method of claim 14, wherein a majority of therestrainer is added during the first 10% of the chewing gum base mixingcycle.
 17. The method of claim 14, wherein a majority of the restraineris added at the start of the chewing gum base mixing cycle.
 18. Themethod of claim 14, wherein the gum base includes less than about 2.0%by weight gum base plasticizer, if any.
 19. The method of claim 14,wherein the gum base includes less than about 2.0% by weight petroleumwax, if any.
 20. The method of claim 14, wherein the restrainerconstitutes about 20-75% by weight of the gum base.
 21. The method ofclaim 14, wherein the restrainer constitutes about 25-55% by weight ofthe gum base.
 22. The method of claim 14, wherein the restrainerconstitutes about 30-40% by weight of the gum base.
 23. The method ofclaim 14, wherein the restrainer has a solubility parameter within about±1.0 S.P.U.'s of the solubility parameter of the free fruit flavoringredient.
 24. The method of claim 14, wherein the restrainer has asolubility parameter within about ±0.5 S.P.U.'s of the solubilityparameter of the free fruit flavor ingredient.
 25. A method of making agum base for use in a free-flavored chewing gum, the chewing gumincluding a free flavor ingredient having a cohesive energy density anda solubility parameter defined as the square root of the cohesive energydensity, the method comprising the steps of:providing a polyvinylacetate restrainer having a solubility parameter within about ±2.0S.P.U.'s of the solubility parameter of the free flavor ingredient, thesolubility parameter of the restrainer defined as: ##EQU4## adding therestrainer into a chewing gum base mixing cycle in an amount sufficientto constitute at least about 10% by weight of the chewing gum to be madefrom the gum base; and blending the restrainer together with at least afiller, an elastomer and a resin to form a chewing gum base.
 26. Themethod of claim 25, wherein the gum base includes less than about 4.0%by weight gum base plasticizer, if any.
 27. The method of claim 25,wherein the gum base includes less than about 2.0% by weight wax, ifany.
 28. The method of claim 25, wherein the gum base includes less thanabout 4.0% by weight gum base plasticizer, if any, and less than about2.0% by weight wax, if any.